<!DOCTYPE html>
<html>

<head>
    <title>Bootstrap 实例</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.0.0-beta/css/bootstrap.min.css">
  
    <style>
        body {
            position: relative;
        }

        .nav {
            top: 100px;
            left: auto;
            right: 0;
            width: 150px;
        }
        .nav li>a{
            color: #ccc;
        }
        .nav li>a.active{
            color: #fff;
        }

        .nav .dropdown-menu {
            color: #333;
        }
    </style>
</head>

<body data-spy="scroll" data-target=".nav" data-offset="50">
    <!-- nav -->
    <ul class="nav flex-column fixed-top bg-dark navbar-dark" >
        <li class="nav-item">
            <a class="nav-link" href="#section1">section1</a>
        </li>
        <li class="nav-item">
            <a class="nav-link" href="#section2">section2</a>
        </li>
        <li class="nav-item">
            <a class="nav-link" href="#section3">section3</a>
        </li>
        <li class="nav-item dropdown">
            <a class="nav-link dropdown-toggle" href="#" id="navbardrop" data-toggle="dropdown">
                Section 4
            </a>
            <div class="dropdown-menu ">
                <a class="dropdown-item" href="#section41">Link 1</a>
                <a class="dropdown-item" href="#section42">Link 2</a>
            </div>
        </li>
    </ul>
    <!-- nav end -->
    <div id="section1" class="container-fluid" style="padding-top:70px;padding-bottom:70px">
        <h1>Section 1</h1>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
    </div>
    <div id="section2" class="container-fluid " style="padding-top:70px;padding-bottom:70px">
        <h1>Section 2</h1>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
    </div>
    <div id="section3" class="container-fluid" style="padding-top:70px;padding-bottom:70px">
        <h1>Section 3</h1>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
    </div>
    <div id="section41" class="container-fluid " style="padding-top:70px;padding-bottom:70px">
        <h1>Section 4 Submenu 1</h1>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
    </div>
    <div id="section42" class="container-fluid bg-info" style="padding-top:70px;padding-bottom:70px">
        <h1>Section 4 Submenu 2</h1>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
        <p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at
            the navigation bar while scrolling!</p>
    </div>
    <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js"></script>
    <script src="https://cdn.bootcss.com/bootstrap/4.0.0-beta/js/bootstrap.min.js"></script>

</body>

</html>